China is a big manufacturing country of construction machinery products, product coating quality as the first element of competition to attract attention from all sides. In order to meet the needs of market competition, many manufacturers have increased their efforts to improve the quality of product coating. While improving the quality of product painting, there are still the following problems in the painting of construction machinery products in China: environmental protection and energy saving are not enough, and the corresponding supporting measures are not perfect; The environmental protection process and equipment supporting the coating production line are still far from meeting the requirements of environmental protection development, and the problem of "three wastes" in the coating industry is serious. Therefore, facing the future, with the increasingly strict national environmental protection regulations, the construction machinery industry must be greatly improved from the process to the equipment, especially the new painting line must be well prepared in the early painting environmental impact analysis. Painting and environmental protection status 1. Painting equipment high degree of standardization of construction machinery painting equipment is very high degree of standardization, and the industry standard is not perfect, so that the standardization is poor. Starting from the design scheme, the painting process and equipment, as well as the corresponding environmental protection equipment are highly flexible, which brings great inconvenience to the manufacturing of manufacturers, the choice of manufacturers and the management of manufacturers. In recent years, equipment such as dust removal equipment, spray booth, spray gun, recycling system has gradually become standardized and serialized; The degree of automatic painting system, intelligent logistics transportation and intelligent control has been greatly improved, and has been applied in the main painting line in our country, so that the technical level and automation level of the painting line in the entire construction machinery industry has been greatly improved. 2. The "three wastes" problem is serious. The "three wastes" problem of construction machinery painting is serious: first, the painting process is backward; The second is the lack of effective pollution control technology, especially the emission reduction and treatment of waste gas. At present, solvent-based coatings still account for about 80% of the total amount of coatings used in construction machinery, causing production environment and atmospheric pollution and resource waste. The development of low-pollution coatings, gradually replacing solvent-based coatings is the development direction of the industry, to speed up the development of low-pollution coatings, we must increase investment in both technical and economic aspects, and the current investment in both aspects are insufficient. In addition, the quality of water-based coatings is not satisfactory, which has become a technical bottleneck of its promotion, and it is necessary to further strengthen the technical development. (1) In the early stage of the painting project, the painting process and equipment of the product, as well as the corresponding environmental protection supporting process and parameters have not been developed, but the conventional estimation is generally carried out, resulting in a large discrepancy between the project implementation and the preliminary environmental planning; (2) The large air volume and low concentration of organic waste gas generated by painting are basically direct high-altitude emissions. Because its concentration is lower than international emission standards, its emission rate is difficult to detect in real time, and environmental protection units generally release it. For some places with high environmental protection requirements, in order to cope with the inspection, intermittent activated carbon adsorption method is used; (3) The degree of automation of painting production is low, and almost all manual spraying operations are used; Construction machinery industry coating professionalism level is poor, many companies generally use the way of outsourcing; The overall painting technology level is low, the application of efficient spraying system is less, a large number of tools with low spraying efficiency are used, and a large amount of waste paint and waste gas are generated while wasting a lot of paint, which also causes serious pollution of painting production line equipment and poor overall environment of the workshop, making the use and maintenance of painting equipment in the industry in a non-virtuous cycle. 4. The painting process update is slow. China's construction machinery industry is still dominated by the traditional three-coating system (primer +2 top paint) in the 1980s. The process is mature and convenient for construction, but VOC(volatile organic compounds) emissions are large. The thickness of the medium paint and top paint accounts for more than 70% of the total thickness of the coating, of which the solvent-based base paint construction solid fraction is only about 15%, the solvent content accounts for 85%, is the main source of VOC emissions. Painting and environmental protection development direction (1) Actively promote the industry's environmental protection work, actively carry out energy conservation and emission reduction, improve the three waste treatment facilities, promote low-pollution coating products and pollution control new technology, vigorously promote and promote low-pollution coatings in the industry (high solid paint, radiation curing paint, water-based paint, powder paint, etc.), especially pay attention to the promotion of water-based paint. The development of environmentally friendly coatings meets the requirements of environmental protection and saves a lot of organic solvents. In recent years, environmental friendly coating varieties have developed rapidly in China, in view of the particularity of construction machinery coating products, only some new varieties have been applied, and need to be further promoted. (2) Actively promote the updating and formulation of industry standards, and the adoption of industry painting and environmental protection standards that are in line with international standards is the premise of changing the backward status quo of industry painting and adapting to environmental development. (3) We must increase investment in energy conservation and emission reduction technologies. In order to effectively reduce VOC emissions, the painting and drying process and equipment should use energy-saving environmental protection equipment, mainly in the following three aspects of implementation: first, for low concentration of paint organic solvent waste gas treatment. Using efficient and high-quality activated carbon fiber as the adsorption medium, the mechatronics efficient waste gas treatment device controlled by microcomputer program has high purification efficiency (up to 95%), compact structure, easy installation and maintenance, and stable and reliable operation. The principle of the device is: the organic waste gas enters the activated carbon fiber adsorption unit through the fan for adsorption, and the purified air is discharged into the atmosphere. After the adsorption unit is saturated, the heat from the upper and lower heat exchange chambers of the catalytic decomposition chamber is sent to the adsorption unit for adsorption through the high-temperature fan. The concentrated organic waste gas after adsorption is returned to the catalytic decomposition chamber through the pipeline for combustion, and the heat generated after combustion is recycled to reduce the electric energy required for catalytic decomposition heating. At present, this device is only used in some large companies, and the investment and operation cost is much lower than that of imported equipment. Second, the high-temperature exhaust gas generated during the drying process of the paint is treated. The paint drying waste gas is treated by direct combustion and then further treated by catalytic combustion. Treatment process: When the high-temperature exhaust gas generated by the drying chamber is introduced into the combustion chamber for treatment, the heat energy is reused through heat exchange, and the post-stage treatment is then catalytic decomposition and combustion, and the heat energy generated after combustion is recycled, while reducing the electric energy required for catalytic decomposition and heating. Third, the use of advanced spraying system to improve spraying efficiency. This is the way and measure to reduce diluent; The use of centralized paint transfer system to reduce the waste of paint and organic solvents and the pollution caused by it; Mixed gas spraying system is used for primer and middle paint, which greatly improves the spraying efficiency and the transfer efficiency is about 75%; The top paint adopts station type conveying paint system and mixed gas electrostatic spraying system, and the spraying transfer efficiency reaches 85%. According to China's "13th Five-Year plan", in order to meet the requirements of environmental protection, should actively develop and use "energy saving, provincial resources, low pollution, high efficiency" paint varieties, namely the so-called "4E" principle (economy, efficiency, ecology, energy). Specifically, it mainly includes water-based coatings, powder coatings, light curing coatings, high solid content coatings and so on. From the painting point of view, mainly to reduce pollution, save energy consumption, improve construction efficiency, improve the decorative coating and the generalization of coating equipment, serialization, automation direction.
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